1. Field of the Invention
This invention relates to a device for feeding particulate materials at a constant feed rate. This invention relates particularly to a constant-rate feeding device capable of feeding different kinds of particulate materials with a predetermined mixing ratio.
2. Description of the Prior Art
I have already proposed in Japanese utility-model publication No.(Sho) 53-6221 a feeding device for particulate materials which comprises a hopper having a bottom surface inclined by more than a rest angle of the particulate materials to be fed, and a feed roller provided near an outlet of the hopper and having a frictional peripheral surface for feeding the particulate materials with friction therebetween during its rotation. There is provided a control gate having a semi-circular section which is rotatable about an axis extending in the axial direction of the feed roller and cooperates with the feed roller to provide a material passing channel therebetween. The particulate material fed through the channel is collected in a chute disposed beneath the feed roller.
With this prior art device, a feed rate of the particulate materials is determined on the basic of the opening degree of the channel and the rotating speed of the feed roller, and may therefore be easily regulated by adjusting the rotational angle of the control gate and/or by changing the feed roller revolution speed. It has been demonstrated that the feeding device of this type operates favorably when the particulate materials to be fed are of a single kind.
In some cases it is necessary to feed two or more different kinds of particulate materials at a predetermined mixing rate. In such a case, in order to maintain the predetermined mixing rate throughout operation, it is necessary to feed the respective kinds of the particulate materials at constant feed rates. It is also to be contemplated that the particulate materials, as mixed at the predetermined mixing rate, should be supplied to the next stage of operation at a predetermined feed rate.
When several different kinds of the particulate materials are to be fed at a given feed rate while being premixed at a given mixing rate, a corresponding number of the feed devices disclosed in my earlier Japanese publication may be employed for the respective kinds, which, however, would result in an extremely large-size equipment and require considerable costs. Moreover, it would be difficult to control separately the control gate positions and/or the feed roller speeds in the respective devices, so as to maintain the predetermined mixing ratio while increasing or decreasing a feed rate or quantity of the particulate materials in the mixed state.
When the aforementioned feed device is applied for continuously feeding a large quantity of the particulate materials, it would be necessary to employ a feed roller having a considerable axial length and a greater diameter. This results in a larger-size device and increases costs for equipment.